http://api.tweetmeme.com/imagebutton.gif?url=http://sports.espn.go.com/boston/nba/news/story?id=6466824&campaign=rss&source=NBAHeadlines (http://api.tweetmeme.com/share?url=http://sports.espn.go.com/boston/nba/news/story?id=6466824&campaign=rss&source=NBAHeadlines&service=bit.ly&source=espn)Boston Celtics captain Paul Pierce expressed remorse Monday for letting his teammates down by getting ejected in the fourth quarter of Sunday's Game 1 loss to the Miami Heat in an Eastern Conference semifinal series.